Process for lead-plating metals



J. C. McCLINTOCK & R. J. SHOEMAKER. PROCESS FOR LEAD PLATING METALS. APPLICATION FILED JUNE 26, 1915.

1,1 95,376. Patented Aug. 22, 1916.

Arm/Mrs PATENT onion, 1

JOHN CALHOUN McGLINTO CK AND BOBER'I JAY SHOEMAKER, OF TOPEKA, KANSAS.

PROCESS FOR LEAD-PLATTNG- METALS.

I Specification of Letters Patent. Patented Aug. 22, 1916 Application filed June 26, 1915. Serial No. 36,466.

To all whom it may concern:

Be it known that we, JOHN C. MoCLIN- TOOK and ROBERT J. SHOEMAKER, citizens of the United States, and residents of Topeka,

The process is based on the fact that metals, after a suitable cleansing of impurities on their surfaces, if dipped into molten lead at a proper temperature will become coated with lead, which adheres the surface of the metal and forms a non-porous and uniform coating. The process of lead plating is greatly improved if the metal is dipped into a molten flux of zinc chlorid previous to its immersion intothe lead bath.

The details of our process will be described in connection with iron or steel; but it is'self-evident that any other metal, the

' melting point of which is above the temperature of the lead bath, can be coated similarly. The iron or steel to be coated with lead is ycleaned from inorganic impurities, and particularly of oxids of iron, by immersing the iron or steel in a bath consisting preferably of equal parts by weight of commercial hydrochloric acid and water. This acid bath is maintained at a temperature of approximately 70 F. Care must be exercised that the metal receiy a thorough cleaning in the bath in order to remove all oxids, as any .oxid remaining on the surface of the iroif acid bath. The caustic solution is preferably caustic soda or potash dissolved in ten parts by weight of water and used at a temperature of approximately 212 F. The iron from the acid bath, while covered with the diluted acid, is plunged into the flux of molten zinc chlorid and then into the molten lead. The temperature of the two baths,

that is, of the flux and of the lead, should be between 640 and680 degrees F. in order to secure satisfactory results. c

Wehave found by experiment that a lead deposit obtained at any other temperature than 640 to 680 degrees F. is not satisfactory. Below 640 the metal does not possess sulficient fluidity to cover the metal uniformly; and above 680 F. the lead oxidizes so rapidly that it is impossible to secure a deposit free from burned spots, pin holes, or other serious defects which expose the surface of the metal coated.

The appended drawing shows diagrammatically a preferred form of a furnace to be used in connection with our process. The

chamber A is heated, preferably by a gaseous fluid fuel to easily regulate the temperature of the molten lead within. Extending slightly below the surface of the lead within the chamber A, and also above the level of the lead, is a frame B of any suitable form and preferably secured to one side of the chamber in the furnace. Said frame forms a compartment for the flux or molten zinc chlorid. The flux, by reason of its density, will flow upon the surface of the lead, and its level above the lead surfaceis controlled by the walls of the frame B. The surface of the lead is kept clean by skimming it with any suitable means. In using this furnace, the metal to be coated, after it is cleaned in an acid bath and while the acid covers the surface ofthe'cleaned metal, is plunged into the compartment B and is held in the zinc chlorid until the temperature of the metal to be coated has reached that of the flux, which is between 640 and 680 degrees Fahrenheit.

When the metal has attained the temperature of the flux, it is plunged perpendicularly into the molten lead which lies lmmediately under the zinc chlorid, that is, the .100

object is forced throu h the opening in the bottom of the frame After the ob]ect enters the chamber A, the same is positioned laterally or diagonally under the partition which separates the compartment B from the chamber A, and the object is then extracted from the chamber A.

It is to be noted that the operatlonpf plunging the material for treatment with zinc chlorid perpendicularly into the molten lead removes all adhering zinc chlorid which flows up through the lead and collects in compartment B. y In this manner the greater chlorid over and over again, and, at the' same time, the metal in compartment A is not contaminated with flux.

l/V'e have found that an alloy of 96% of lead, 2% of antimony, and 2% of tin when deposited upon iron or steel produces a coating of greater hardness, tensile strength, and more crystalline than lead alone, and by the term lead as used in the claims we intend to include ordin ary lead alloys, such, as for example as that just specified. It is also to be remarked that the melting point of this alloy is lower than that of lead.

It is self-evident that the entire process can be carried out by mechanical means in a manner similar to the galvanizing and tinning processs.

Our process can be efiiciently applied to the coating of sheet metal, pipe, boiler fiues, raw wire, worked wire, etc.

While We have described the principle of operation, together with the process which We now consider to be the best embodiment thereof, we desire to have it understood that the process shown is merely illustrative and that such changes may be made as are within the scope of the appended claims.

We claim:

1. A lead-plating process for metals, consisting in cleaning the surface of the metal with an acid, immersing the metal .so cleaned, and while it is covered with the acid film, into 'a molten flux, maintaining the metal immersed until the temperature thereping the metal into a bath of molten lead, which bath is at a temperature substantially that of the flux.

2. A lead-plating process for metals, consisting in submerging the metals iii hydro-.

chloric acid to remove all oxids therefrom, then immersing the metal, while it is covered by a film of acid, into molten flux of zinc chlorid supported by a molten lead bath, the temperature of the bath being maintained between 640 and 680 Fahrenheit, maintaining the metal in the flux until its temperature is that of the flux, then lowering the metal into the lead below the flux and extracting the metal from the bath where its surface is clear of the flux.

In testimony whereof We have signed our names to this specification in the presence of two subscribing witnesses.

JOHN CALHOUN McOLINTOOIQ ROBERT JAY SHOEMAKER.

Witnesses: I

W. D. BOUGHTON, FRANCES SHOEMAKER.

40 of rises to that of the molten flux, then dip- 

